Welcome to the MCS650X product family. This manual is designed to work in conjunction with the Hardware Manual which describes the basic hardware considerations when using the MOS Technology, Inc. microcomputer family.

Before reading this manual, it is suggested that the reader acquaint himself with the Hardware Manual in order to understand the components available in this system, how these components are interconnected, and their basic architecture. Developed in this manual is the concept of microprocessor internal architecture and how it is used, with attention given to input/output considerations. Familiarity with the hardware will facilitate easier understanding of these important concepts. 

In order to best serve the total customer base, this manual is written in two levels. The first is a very basic introduction to the MCS650X family, and the second level is for the user who has to refer to the manual on more than an occasional basis and who wants to rapidly scan and find specific sections. For the user who is quite familiar with programming and the MCS650X instruction set, the appendices are the best reference in the sense that all the data which is discussed in detail in the manual is summarized in a series of tables for convenience. 

It is recommended that the user who is an experienced programmer and familiar with microprocessors still take the time to read through the manual in detail. Some of the architectural concepts are different from those found in second generation machines and this manual instructs the user how to optimize the utilization of the microprocessor while providing an introduction of its basic concepts.

Criticism of this manual is welcomed at all times. Of particular interest are cases where one could not, by use of the index and appendix, rapidly find the answer to a question which developed in the course of designing a microprocessor system. Welcomed are any comments which will enhance the content and format of this manual in future editions or addendums.